A Risk Science Perspective on Vaccines

"The main goal of the risk characterization and communication should be to provide people with a fair and honest representation of the relevant risks, also respecting differences in points of views among experts as well as between professional judgments of risk, and lay people's perceptions of risk."

Although health experts and agencies argue that vaccines are safe and that the benefits of vaccines clearly outweigh the possible side effects, many people remain hesitant as they consider the risk imposed by the vaccine larger than the risk related to the disease. By using a contemporary risk perspective as the basis, this article looks at the way risks in relation to vaccines are - and should be - understood, assessed, characterised, communicated, and handled. The analysis distinguishes between two categories of vaccination risk: (i) the risk related to contracting the disease, with and without the vaccine and (ii) the risk related to side effects of the vaccine. The article highlights principles and approaches from risk science that are applicable to a wide range of risk problems.

Following an introduction, Section 2 provides an overview of some key events and cases related to vaccines and vaccination risks throughout history, the aim being to point to what the authors consider important foundational issues. A key theme in several of the cases referred to in this section is the dimension of time (e.g., swift vaccine development) and how it affects the understanding and assessment of the consequences and uncertainties associated with vaccination. Also fundamental is the role of trust - or lack thereof - in issues concerning vaccine risk understanding and communication. Furthermore, the review points to several instances where governments and public health authorities had to balance the promotion of vaccine uptake with clear and honest descriptions of the risks and uncertainties involved. This delicate balance, along with the herd immunity concept, which requires individuals to weight the risk to themselves against community benefits, exemplifies the differences in perspectives between individuals and the society when it comes to making decisions concerning vaccine risks.

Section 3 conceptualises risks related to vaccine and vaccination using a contemporary risk perspective, which is described is documents produced by the Society for Risk Analysis (SRA). Risk science, according to this body of literature, can be defined as the practice that provides us with the most justified beliefs that can be produced at the time being on the subject matter covered by the risk field, covering concepts, principles, approaches, methods, and models for understanding, assessing, characterising, communicating, and managing risk. From this perspective, the risk related to an activity has two main components: the future consequences C of the activity and uncertainties U related to C. For short, the authors refer to the risk as (C,U). When considering risk related to vaccines and vaccination, the activity is life in the area considered (societal perspective) or the life of a particular person (individual perspective). The activity is observed in a period of time, say [0,T]. There are a number of relevant aspects take into account when addressing vaccination risks. For example, the development and distribution of vaccines could introduce ethical and social risks, as seen in discussions concerning vaccine accessibility for vulnerable populations and low-income countries.

Section 4 provides a discussion of foundational issues from the historical review in light of the conceptual framework presented in Section 3, particularly focusing on issues related to COVID-19. From a societal point of view, herd immunity is essential for protecting vulnerable populations and reducing the overall spread of the disease. However, both vaccination and contracting the disease carries risks for the individual, and thus, achieving herd immunity requires balancing a tradeoff between individual risks and community benefits. There is a difference in the consequences (quantities) of interest in the professional risk judgments made by the public health authorities and other institutions, versus those in individual risk judgments. Moreover, variations could exist also among the public agencies and institutions, as they may have different priorities, values, and objectives. In this context, trust and skepticism are considered core concepts in contemporary risk science literature and play an important role in shaping people's understanding, perception, and response to various types of risks, not only those related to vaccines.

Using the risk conceptualisation and framework presented in Section 3, the critical issue is that the knowledge K with COVID-19 vaccination is rather weak (as of early 2021) concerning the side effects of the vaccine, particularly when it comes to the rare and long-term consequences. Several of the examples in Section 2 illustrate the importance of considering how changes in knowledge over time can affect judgments of risk associated with vaccination. The issue is also relevant in relation to updating policies as new knowledge becomes available. Thus, the authors point to the importance of taking the aspect of time and the dynamic development of knowledge into account in the handling of vaccine risks, ensuring that decisions are revisited when new knowledge emerges.

Section 5 provides some final remarks and conclusions. In December 2021, the White House in the United States communicated that "...For the unvaccinated, you're looking at a winter of severe illness and death for yourselves, your families and the hospitals you may soon overwhelm". Per the authors, this statement does not inform people about risk, as it is deterministic: Uncertainties and likelihood judgments are ignored. "The statement was probably motivated by a policy to frighten people to take the vaccine - the goal of the communication was to get people vaccinated, and that was seen as more important than communicating risk in a neutral and balanced way. People were not risk-informed by this message." In the authors' view, this approach did not represent prudent risk science in that people could quickly lose trust in the authorities (if not already lost), "as the message is considered biased and to represent misinformation. Risk science and risk communication promote characterizations of risk that should aim at improving people's risk understanding. Then, deterministic messages like this should be avoided."

Instead, the authors urge that people be viewed as capable of understanding messages that involve statements about risk, uncertainties, likelihood, and knowledge. The messages need to be delivered in a professional way, building on risk science knowledge. Risk-related information should be provided in a way that is sensitive to the concerns of the audience, including their level of skepticism. People may have different concerns about vaccination that go beyond the safety and effectiveness of the vaccines. Addressing these concerns, and understanding how they affect trust and skepticism, is important in order to ensure that information concerning risk is effectively communicated and understood. Furthermore, the communication needs to be faithful in its representation of the relevant risks, avoiding messages that express misrepresentations of information in order to achieve an objective, even if the objective is well intentioned.

In what follows, the authors present some characterisations they consider to be prudent risk science and risk communication. The examples are not tailored to a particular communication situation but are intended to serve as suggestions for how risk-related information should be presented, reflecting the ideas and discussions in previous sections. In addition, Table 2 provides an overview of the key issues raised in relation to vaccination risks and outlines the main contributions of the article in addressing these issues. The contributions build on principles and approaches from contemporary risk science knowledge.